Method and process of contract to a heat softened solder ball array

ABSTRACT

A method for enhancing temporary solder ball connection comprises the application of thermal energy to the solder balls, heating them to a submelting “softening” temperature, whereby the compression force required to connect all balls in a BGA is achieved at much reduced force, avoiding damage to the package, insert, substrate and support apparatus. Several forms of heating apparatus, and temperature measuring apparatus are disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 09/145,832,filed Sep. 2, 1998, now U.S. Pat. No. 6,121,576, issued Sep. 19, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to semiconductor chip packages. Moreparticularly, the present invention pertains to methods for electricalcontact of an array of solder balls with a noncompliant surface.

2. State of the Art

The testing of packaged semiconductor devices has always presentedproblems to device manufacturers. Various types of tests may beconducted at different stages of manufacture. In the current state ofthe art, “wafer sort” electrical tests may be conducted prior topackaging to determine nonworking dies. Following packaging, varioustests including environmental tests as well as parametric and functionalelectrical tests may be performed. A final test which is known as“burn-in” may optionally be conducted. The test includes temperaturecycling over an extended period of time. Essential to the testing ofindividual dies is reliable electrical connection of all die leads tothe test board, without incurring damage to the die or testingapparatus, and easy disassembly from the testing apparatus. While“permanent” wire connections are widely used, wirebonding is timeconsuming and expensive, and also makes the matching of device impedanceto the substrate impedance very difficult to achieve. Much effort isbeing spent on developing alternative methods to reduce the time andexpense of using wire bonds. The replacement of wire bonds with ballgrid array (BGA) connections is becoming more common. Temporaryconductive attachment of solder balls to e.g. a test board is less thansatisfactory.

Temporary connection of device circuits to a test apparatus is known topresent a variety of problems. The insert member into which asemiconductor die is placed for testing is typically noncompliant, i.e.ceramic or silicon, for example.

The current method for joining a ball grid array (BGA) to anoncompliant, i.e. rigid surface such as a silicon micromachined pocketinterconnect or insert, is to apply, at ambient temperature, arelatively high compression force of about 22-30 grams-force per solderball. Theoretically, all balls of the array should be pressed intomechanical and electrical contact with the insert pocket. The use ofcompressive forces lower than the above results in a further increasedfrequency of unsatisfactory electrical connections.

The presence of such unconnected solder balls in a BGA attachment formedunder ambient conditions is believed to be due to a significantvariability in ball diameter and “height” which the industry has beenunable to eliminate. As a result, the applied force of about 22-30grams-force or even more per ball is, in practice, insufficient toensure the required contact of all balls of the array. Furthermore, theuse of compression forces in excess of about 30 grams-force tends todamage the underlying material of the die, insert, and/or substrate. Forexample, effective connection of a 48 ball BGA array using solder ballsof a nominal diameter may require in excess of about 1.5 kg-force. Suchpressures exerted on a die for connection to a ceramic insert may damagethe die and/or insert and/or substrate below the insert. The total forcerequired for connection of larger arrays will be even more. In addition,the use of larger balls not only increases the absolute variation inball diameter but the force required to sufficiently deform each ballfor establishing the required temporary electrical connection. Theproblem also exists with smaller solder balls such as comprise a fineball-grid-array (FBGA) of 0.0125 inches (0.325 mm) diameter balls, forexample. With the smaller diameter solder balls, variation in ballplacement location may have a greater effect than nonuniform balldiameters.

To date, the industry has continued to use relatively high compressiveforces and necessarily accepted the increased occurrence of electricalconnection failures of a BGA and/or damage to the die, insert orsubstrate.

Ball grid arrays are used in a variety of semiconductor devices.Illustrative of such prior art are U.S. Pat. No. 5,642,261 of Bond etal., U.S. Pat. No. 5,639,695 of Jones et al., U.S. Pat. No. 5,616,958 ofLaine et al., U.S. Pat. No. 5,239,447 of Cotues et al., U.S. Pat. No.5,373,189 of Massit et al., and U.S. Pat. No. 5,639,696 of Liang et al.

Semiconductor devices having dual sets of outer “leads”, e.g. twin BGAsurfaces or a combination of e.g. J-leads and solder bumps, are shown inU.S. Pat. No. 5,648,679 of Chillara et al., U.S. Pat. No. 5,677,566 ofKing et al., and U.S. Pat. No. 5,668,405 of Yamashita.

Chip carriers of several configurations are described in U.S. Pat. No.4,371,912 of Guzik, U.S. Pat. No. 4,638,348 of Brown et al., andJapanese publication 60-194548 (1985).

Semiconductor devices joined in stacks are disclosed in U.S. Pat. No.4,868,712 of Woodman, U.S. Pat. No. 4,841,355 of Parks, U.S. Pat. No.5,313,096 of Eide, U.S. Pat. No. 5,311,401 of Gates, Jr. et al., U.S.Pat. No. 5,128,831 of Fox, III et al., U.S. Pat. No. 5,231,304 ofSolomon, and U.S. Pat. No. 4,956,694 of Eide.

U.S. Pat. No. 5,637,536 of Val discloses a chip stacking configurationwith solder ball connections.

U.S. Pat. No. 5,012,323 of Farnworth discloses a dual-die package havingwire interconnections.

U.S. Pat. No. 4,761,681 of Reid discloses a multi-chip device havingelevated (conductor covered mesa) interconnections.

Despite the advanced state of the art in lead interconnection, devicepackaging and testing, the temporary connection of semiconductor devicesto testing apparatus and burn-in boards remains an area which needsimprovement.

BRIEF SUMMARY OF THE INVENTION

The present invention pertains to methods for electrical contact of anarray of solder balls with a noncompliant surface, that is, themechanical and electrical contact of a ball grid array (BGA) to arelatively noncompliant contact set such as a silicon micromachinedpocket interconnect (i.e. “insert”) for a test pad or bum-in board(BIB).

The present invention further provides a reliable BGA connection methodand apparatus whereby the required pressure is much reduced to eliminateor significantly reduce compression-caused damage to the die, insertand/or substrate.

The present invention comprises methods and apparatus for softeningsolder bumps or balls so that all of the bumps/balls in an array readilyconform to a matching array of conductive contact pockets or pads inanother body. The array of solder bumps/balls is heated to a softeningtemperature lower than the melting point of the solder and quicklyplaced in slightly compressed engagement with the contact pockets orpads of a substrate. As compared to joining the arrays at ambienttemperature, all bumps/balls of the BGA are reliably connected, and theconnection is achieved at a much reduced pressure, avoiding damage tothe die and/or substrate. In addition, much less stress is placed on theapparatus holding the packaged die, the insert and test board.

The softening temperature to which the solder is heated is below themelting temperature of the solder alloy.

A variety of heating apparatus and methods is disclosed, includingdirect heating of the bumps/balls, heating of the entire assembly,heating of a chuck holding the IC, heating of a chuck holding theinsert, direct heating of the insert or substrate, etc. A temperaturesensing circuit may also be incorporated into the insert, substrate, orsubstrate retaining socket for the purpose of measuring and controllingthe temperature to which the bumps/balls are heated.

While electrical contact is readily maintained during electrical testsor burn-in by maintaining a small compressive force, ball contact iseasily removed by discontinuing the compressive force and lifting theBGA from the insert or substrate to which it was electrically connected.

The invention is applicable to a wide variety of solder compositions,solder bump designs and ball diameters.

Other features of the invention will become clear from study of thefollowing description and related figures.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The invention is illustrated in the following figures, wherein theelements are not necessarily shown to scale:

FIG. 1 is a perspective view of an insert assembly for the electricaltesting of a typical flip-chip semiconductor package with BGA, whereinheat enhancement of the BGA connection in accordance with the inventionis shown;

FIG. 1A is an edge view of a ball grid array on a semiconductor chip;

FIG. 2 is a perspective view of an insert assembly for the electricaltesting of a typical flip-chip semiconductor package with BGA, showingthe package in compressive engagement with the insert assembly forheating enhancement of the BGA connection in accordance with theinvention;

FIG. 3 is a plan view of a substrate member of the invention;

FIG. 4 is a bottom view of a substrate member of the invention;

FIG. 5 is a cross-sectional view of a portion of a heating assembly ofthe invention; and

FIG. 6 is a cross-sectional view of various solder ball contact sites towhich the invention may be applied.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to method and apparatus embodiments forthe uniform temporary electrical connection of solder bumps, e.g. solderballs, of a semiconductor device to another body. Rapid thermalsoftening of the solder bumps may be achieved by a variety of specificmethods and apparatus, as described herein. The methods are particularlyuseful for attachment of solder bumps to the surface of a noncompliantbody such as formed of silicon, ceramic, etc.

As shown in drawing FIG. 1, a semiconductor package 10 is exemplified bya flip-chip package (FCP) with a ball grid array (BGA) 30 of a pluralityof solder bumps or balls 12 on one surface 14 of the semiconductorpackage 10.

A test apparatus for evaluating circuit performance of the semiconductorpackage 10 is shown as including an insert 16 and a substrate member 18.The insert 16 is noncompliant and is typically formed of ceramic orsilicon with a pattern of electrical contact sites 20 micromachined onits upper surface 22. The contact sites 20 may comprise simple planarpads, or contact pockets of any configuration, as explained infra. Thecontact sites 20 are connected by conductive traces, not visible, tobond pads 24, the latter being connected by wire bonds 26 to conductivetraces 28 on the substrate member 18. The wire bonds 26 and traces 28 onthe insert 16 and substrate member 18 may be encapsulated in resin forprotection. Other means for connecting the contact sites 20 to acontroller conducting a test, burn-in, etc. may be used, as known in theart.

The substrate member 18 and attached insert 16 are typically insertedinto a socket on a test fixture or a burn-in-board (BIB), neither shownin drawing FIG. 1.

In accordance with the invention, the ball grid array 30 of solderbumps/balls 12 is heated and compressed under a slight pressure into thecontact sites 20, shown here as indentations or pockets. The solderbumps/balls 12 are heated to a submelting softening temperature T_(s)and are uniformly contactable to the contact sites 20 by an increaseddeformation under the slight compression force.

In one simple embodiment, an external heater 40 emitting infraredradiation or heated air 42 is positioned to heat the semiconductorpackage 10 including the solder bumps/balls 12 to the desired softeningtemperature, and the BGA 30 is quickly inserted and compressed by force38 into engagement with the contact sites 20 at a relatively lowpressure such as about 2-10 g-force per solder bump/ball 12. Referringto drawing FIG. 1A, of course, the required force per solder bump/ball12 will vary, depending upon the softening characteristics of theparticular solder composition used, the temperature to which the solderbumps/balls 12 are heated, the nominal ball diameter 32, the maximumvariation in ball diameter 32 and the variation in drop distance 34between ball centers 34A and the surface 14 of semiconductor package 10.Typically, the required force 38 at the softening temperature T_(s) toachieve complete ball connection is about 8-25 percent of the force atambient temperature.

Instead of directly heating the semiconductor package 10 to soften thesolder bumps/balls 12, heat may be applied to the insert 16 or substratemember 18 before connecting the BGA 30 to the contact sites 20. Also,the semiconductor package 10 may be indirectly heated by applyingthermal energy to a chuck, not shown, which holds the package.

As shown in drawing FIG. 2, a semiconductor package 10 with an array ofsolder bumps/balls 12 is placed on an insert 16, and placed under acompression force 38. Thermal energy is applied either to the back side36 of the semiconductor package 10, to the insert 16, to the substratemember 18 (as shown in FIGS. 4 and 5), to a compression member, notshown, compressing the back side of the semiconductor package 10 withforce 38, or to a socket, not shown, which surrounds the substrate.

Alternatively, the assembly of semiconductor package 10, insert 16 andsubstrate member 18, together with compression and support apparatus,may be placed in a temperature controlled oven and rapidly heated to thedesired softening temperature T_(s).

Thus, the solder bumps/balls 12 may be heated by conduction, convectionor radiation, or any combination thereof. For example, an externalheater 40 (FIG. 1) may heat the semiconductor package 10, insert 16,substrate member 18, or a socket into which the substrate member fits byradiation or heated air 42.

The solder bumps/balls 12 may be of any diameter 32, including those ofa fine ball grid array (FBGA), where the balls have a pitch of less thanone (1) mm.

The solder bumps/balls 12 may be formed of various solder compositions,including tin-lead solders having a lead content of about 30 to 98percent. Solder compositions having the higher lead concentrations oftenhave a higher melting point.

A softening temperature T_(s) of about 130 to about 180 degrees C. hasbeen found useful for reducing the compression force 38 to a relativelylow value and simultaneously ensuring electrical contact of all solderbumps/balls 12.

As shown in drawing FIG. 3, resistive heating elements 44 may be appliedto the top surface 48 of the substrate member 18, preferably under theinsert 16 and substantially beneath the semiconductor package 10. Theheating elements 44 are shown as having power leads 54, 56 for providingsufficient power to quickly heat the insert 16 including the electricalcontact sites 20, not shown, and the solder bumps/balls 12, not shown,which are in engagement with the contact sites 20.

All of the conductive traces on substrate member 18, includingconductive traces 28, heater power leads 54, 56, and heating elements 44may be formed simultaneously by screening a thick film of conductivematerial onto the substrate member. This method of forming conductivetraces on a surface is well known in the art.

A thermocouple junction 50 or other temperature detecting device may beinstalled in or on the insert 16 or substrate member 18 for obtainingtemperature feedback and controlling the bump/ball temperature to attaina maximum desired softening temperature T_(s). Thus, for example, asshown in drawing FIG. 3, a temperature sensor 50 (such as thermocouplejunction) may be fixed on the top surface 48 of the substrate member 18or back side 52 (FIGS. 1 and 2) of the insert 16, and have thermocoupleleads 58 connected through otherwise unused conductive traces 28A, 28Bto measurement/control instrumentation, not shown. In use, a heathercontroller, not shown, determines the measure temperature and shuts off(or reduces) power to the heating elements 44 upon sensing apredetermined temperature. A recorder, not shown, may be used tocalibrate the measurements such that a desired softening temperature maybe precisely attained.

A short heating time is preferred, extending only several seconds orless. Most preferably, the heating time is less than one second. Thus,the power leads 54, 56 to the heating elements 44 must be sufficientlylarge to carry the necessary electrical load. In general, installationof the heating elements 44 on the insert 16 will require separate powerleads 54, 56. Normally, wire bonds 26 (FIG. 1) are incapable of carryingthe necessary load.

Another form of heating apparatus which may be used in the invention isillustrated in drawing FIGS. 4 and 5. The substrate member 18 has on itsback side (underside) 46 a pattern of heating elements 44 with junctions62, 64. The junctions 62, 64 may be planar pads or conductively surfacedindentations in the back side 46.

As shown in drawing FIG. 5, a semiconductor package 10, insert 16, andsubstrate member 18 are positioned in a socket 66 on a test board 70.Test board 70 may be a board for an electrical test, for burn-in, orother purpose. The socket 66 is typically formed with walls 68 and base72, and many sockets 66 may be mounted on a single test board 70 toenable simultaneous testing or burn-in of many semiconductor packages10.

A pair of through-holes 74, 76 is formed in the test board 70 along axes84, 86, the axes which pass through junctions 62, 64, respectively. Twometal spring-loaded compression pins 80, also known as “pogo pins”, aremounted in the test board 70 or in another substrate 90 underlying thetest board. Substrate 90, having a plurality of pogo pins 80 projectingtherefrom, is known as a bed-of-nails (BON). The pogo pins 80 have abase 78 and a spring loaded pin 82 which is axially movable relative tothe base 78. The pins 82 are shown passing through-holes 74, 76 toelectrically contact the junctions 62, 64 when in compression, powerleads 92, 94 from the two pogo pins 80 providing sufficient electricpower to the heating elements 44 for rapidly heating the solderbumps/balls 12. Following testing, the spring-loaded pogo pins 80 willpush the substrate member 18 from the socket 66 with a short stroke.

In drawing FIG. 6, several types of BGA contact sites 20 are shown asexamples illustrating the wide variety of solder bumps/balls 12 andcontact sites 20 combinations whose temporary connection is enhanced byuse of an elevated submelting softening temperature T_(s). Each solderbump/ball 12 attached to semiconductor package 10 is configured to be incompressive conductive contact with a contact site 20.

Contact site 20A comprises a flat pad or surface of the insert 16.

Contact site 20B is a spherical indentation in the insert 16.

Contact site 20C is a shallow spherical indentation.

Contact site 20D is a spherical indentation having a central axiallydirected projection 96 which punctures and enters the softened solderbump/ball 12. Preferably, the projection 96 is pyramidal in shape.

Contact site 20E is a spherical indentation having several, typicallyfour, peripheral projections 98 which contact and are forced into thecircumferential surface of the solder bump/ball 12.

The illustrated contact sites 20 to which the invention may be appliedare exemplary only and not exhaustive.

It is clear that a wide variety of apparatus may be used for heatingball-grid-array connections, of which those described herein arerepresentative.

The invention has been illustrated in application to the testing of aflip-chip device. However, the temporary BGA connection of any device,including other chip scale packages (CSP), is enhanced by this processand apparatus.

It is apparent to those skilled in the art that various changes andmodifications, including variations in heating procedures andstructures, may be made to the BGA connection method and apparatus ofthe invention as described herein without departing from the spirit andscope of the invention as defined in the following claims.

What is claimed is:
 1. A method for making contact between an array ofsolid conductive solder bumps on a semiconductor device a plurality ofconductive contact sites on a surface of a first member, comprising:heating at least one solder bump of said array of solid conductivesolder bumps to a softening temperature T_(s) below a meltingtemperature of said at least one solder bump of said array of solidconductive solder bumps; and contacting at least one conductive contactsite of said plurality of conductive contact sites by said at least onesolder bump of said array of solid conductive solder bumps of saidsemiconductor device using a pressure less than substantially 22grams-force for the at least one solder bump and another solder bumpsaid array of solid conductive solder bumps.
 2. The method of claim 1,wherein said melting temperature of said array of solid conductivesolder bumps is T degrees C higher than an ambient temperature T_(o),and wherein the softening temperature T_(s) is about 0.5T-0.95T abovethe ambient temperature T_(o).
 3. The method of claim 1, wherein said atleast one solder bump of said array of solid conductive solder bumpscontacts said at least one conductive contact site of said plurality ofconductive contact sites at a pressure not substantially exceeding about10 grams-force.
 4. The method of claim 1, wherein said at least onesolder bump of said array of solid conductive solder bumps contacts saidplurality of conductive contact sites at a pressure of about 2-10grams-force.
 5. The method of claim 1, wherein said semiconductor devicehaving said array of solid conductive solder bumps is directly heated byone of hot air convection and infrared radiation.
 6. The method of claim1, wherein said first member having said plurality of conductive contactsites is directly heated by said one of hot air convection, conductionfrom a heated object, and said infrared radiation.
 7. The method ofclaim 1, wherein said semiconductor device and said first member areplaced in a temperature controlled oven for heating to the softeningtemperature T_(s).
 8. The method of claim 1, wherein said semiconductordevice is held in a chuck, and said chuck is heated.
 9. The method ofclaim 1, wherein said first member is held in a chuck, and said chuck isheated.
 10. The method of claim 1, wherein said at least one solder bumpof said array of solid conductive solder bumps of said semiconductordevice contacts said at least one conductive contact site of saidplurality of conductive conductive contact sites of said first memberbeing subsequently heated under compressive force to soften said atleast one solder bump of said array of solid conductive solder bumps forconnection to said at least one conductive contact site of saidplurality of conductive contact sites.
 11. The method of claim 1,wherein said first member having said plurality of conductive contactsites is heated by electrical resistance wires.
 12. The method of claim1, wherein said first member and a substrate are mounted on a mountingboard having an integral heater, and said integral heater is controlledto heat said first member to said softening temperature T_(s).
 13. Themethod of claim 1, wherein said array of solid conductive solder bumpscomprise Sn-Pb solder having a lead content of about 40 to about 98percent, and said softening temperature T_(s) comprises about 140 -180degrees C.
 14. The method of claim 1, wherein said heating comprisespredetermining a heating time X to heat said at least one solder bump ofsaid array of solid conductive solder bumps to said softeningtemperature T_(s), and heating for said time X.
 15. The method of claim1, wherein said heating comprises initiating said heating, measuring atemperature of one of an insert, a die, and a substrate being heated,and stopping said heating to limit the temperature of said at least onesolder bump of said array of solid conductive solder bumps to no morethan said softening temperature T_(s).
 16. A method to temporarilyengage at least one conductive solder bump of an array of conductivesolder bumps on a semiconductor device with at least one conductivecontact side of a plurality of conductive contact sites on a surface ofa first member, comprising: heating said at least one conductive solderbump of said array of conductive solder bumps to a softening temperatureT_(s) below a melting temperature of said at least one conductive solderbump of said array of conductive solder bumps; and compressing said atleast one conductive solder bump of said array of conductive solderbumps on said semiconductor device to said at least one conductivecontact site of said plurality of conductive contact sites at a pressureless than substantially 22 grams-force and another solder bump of saidarray of conductive solder bumps.
 17. The method of claim 16, whereinsaid melting temperature of said at least one conductive solder bump ofsaid array of conductive solder bumps is T degrees C higher than anambient temperature T_(o), and wherein said at least one conductivesolder bump of said array of conductive solder bumps is heated to asoftening temperature T_(s) of about 0.5T-0.95T above the ambienttemperature T_(o).
 18. The method of claim 16, wherein said at least oneconductive solder bump of said array of conductive solder bumps iscompressed to said at least one conductive contact site of saidplurality of conductive contact sites at a pressure not exceeding about10 grams-force.
 19. The method of claim 16, wherein said at least oneconductive solder bump of array of conductive solder bump is compressedto said at least one conductive contact site of said plurality ofconductive contact sites at a pressure of about 2-10 grams-force. 20.The method of claim 16, wherein said semiconductor device having saidarray of conductive solder bumps is directly heated by one of hot airconvection and infrared radiation.
 21. The method of claim 16, whereinsaid first member having said plurality of conductive contact sites isdirectly heated by said one of hot air convection, conduction from aheated object, and said infrared radiation.
 22. The method of claim 16,wherein said semiconductor device and said first member are placed in atemperature controlled oven for heating to the softening temperatureT_(s).
 23. The method of claim 16, wherein said semiconductor device isheld and heated for transfer to said semiconductor device.
 24. Themethod of claim 16, wherein said first member is held and heated forheat transfer to said first member to heat said at least one conductivecontact site of said plurality of conductive contact sites.
 25. Themethod of claim 16, wherein said at least one conductive solder bump ofsaid array of conductive solder bumps of said semiconductor device iscompressed to said at least one conductive contact site of saidplurality of conductive contact sites of said first member beingsubsequently heated under compressive force to soften said at least oneconductive solder bump of said array of conductive solder bumps forconnection to said at least one conductive contact site of saidplurality of conductive contact sites.
 26. The method of claim 16,wherein said first member having said plurality of conductive contactsites is heated by electrical resistance wires.
 27. The method of claim16, wherein said first member and a substrate are mounted on a mountingboard having an integral heater, and said integral heater is controlledto heat said first member to said softening temperature T_(s).
 28. Themethod of claim 16, wherein said array of conductive solder bumpscomprise Sn-Pb solder having a lead content of about 40 to about 98percent, and said softening temperature T_(s) comprises about 140-180degrees C.
 29. The method of claim 16, wherein said heating comprisespredetermining a heating time X to heat said array of conductive solderbumps to said softening temperature T_(s), and heating for said time X.30. The method of claim 16, wherein said heating comprises measuring thetemperature of one of an insert, a die, and a substrate being heated,and stopping said heating to limit the temperature of said array ofconductive solder balls to said softening temperature T_(s).
 31. Anapparatus who used to temporarily connect at least one solder ball of aball grid array of solder balls during connection to at least oneconductive contact site of a plurality of conductive contact sites, saidapparatus comprising: a first member with a surface having an array ofsolder balls thereon; a second member with a surface having an array ofconductive contact sites; apparatus for contacting said first memberagainst said second member for electrical contact of said at least onesolder ball of said ball grid array of solder balls to said at least oneconductive contact site of said plurality of conductive contact sites,said first member contacting said second member at a pressure less thansubstantially 22 grams-force for said at least one solder bump andanother solder bump of said ball grid array of solder bumps; and heatingapparatus for heating said at least one solder ball of said ball gridarray of solder balls and said at least on conductive contact site ofsaid plurality of conductive contact sites to a submelting soldersoftening temperature T_(s).
 32. The apparatus of claim 31, wherein eachof said plurality of conductive contact sites comprises a flat surface.33. The apparatus of claim 31, wherein each of said plurality ofconductive contact sites comprises a recess for receiving a portion of asolder ball.
 34. The apparatus of claim 31, wherein each of saidplurality of conductive contact sites comprises a recess having at leastone projection therein for deforming a solder ball inserted therein. 35.A testing apparatus used to test a semiconductor package having a ballgrid array of solder balls on a surface thereof, said apparatuscomprising: an insert formed of generally noncompliant material, saidinsert having a first surface including an array of conductive contactsites for electrical contact with said ball grid array of solder balls,and having a second surface; a substrate having a first surface, havinga second surface, said second surface of said insert secured to saidfirst surface of said surface, and having a pattern of conductive leadson said substrate for connection to contact leads in a socket;electrical leads connecting said array of conductive contact sites ofsaid insert with said pattern of conductive leads of said substrate; atest board having said socket with said contact leads to a testingcircuit, said substrate and insert insertable into said socket forcontact of said array of conductive leads of said substrate with saidcontact leads of said socket; and heating apparatus associated with oneof said substrate, said insert and said socket.
 36. The apparatus ofclaim 35, further comprising: power supply leads providing electricalpower to said heating apparatus.
 37. The apparatus of claim 35, whereinsaid heating apparatus comprises resistance conductors.
 38. Theapparatus of calim 35, further comprising a switch apparatus for turningsaid heating apparatus on and off.
 39. The apparatus of claim 35,further comprising temperature sensing apparatus attached to one of saidsubstrate, said insert, and said semiconductor package.
 40. Theapparatus of claim 39, further comprising a temperature controllerreceiving signals from said temperature sensing apparatus andcontrolling said heating apparatus.
 41. The apparatus of claim 39,wherein said temperature sensing apparatus comprises a thermocouplejunction.
 42. The apparatus of claim 35, wherein said heating apparatus,said power supply leads and conductive leads are simultaneously formedon said substrate.
 43. The apparatus of claim 36, wherein said heatingapparatus, said power supply leads and conductive leads aresimultaneously formed on said substrate.
 44. An apparatus used totemporarily connect at least one solder ball of a plurality of solderballs of a solder ball array on a first member to a correspondingcontact site of a plurality of contact sites on a second member, saidsecond member connected to a third member, said apparatus comprising: aboard having a socket thereon for accepting said first member, secondmemberm, and third member, said board having at least two through-holesextending therethrough; an heating conductor mounted on an underside ofsaid third member; spring-loaded pogo pins mounted to project a pinportion upwardly through each of said at least two through-holes tocontact said third member; and power leads connecting each pogo pin ofsaid spring-loaded pogo pins to a power supply for heating said firstmember, second member, and third member including at elast one solderball of said plurality of solder balls of a solder ball array and atleast one corresponding contact site of said plurality of contact sites.45. The apparatus of claim 44, further comprising a temperature sensormounted within said first member, second member, and third memberconductively connected to a temperature measuring circuit.
 46. A heatingapparatus used to heat at least one solder ball of a ball grid array ofsolder balls while subjected to a compression force against at least oneconductive contact site of a plurality of conductive sites for temporaryelectrical contact, said apparatus comprising: a first member having asurface having an array of solder balls thereon; a second member havinga surface having an array of conductive contact sites; apparatus forcompressing said first member against said second member to contact saidat least one solder ball of said ball grid array of solder balls withsaid at least one contact site of said plurality of contact sites, saidfirst member compressed against said second member at a pressure lessthan substantially 22 grams-force per solder ball; and heating apparatusfor heating said at least one solder ball of said ball grid array ofsolder balls and said at least one conductive contact site of saidplurality of contact sites to a submelting solder softening temperatureT_(s).
 47. The apparatus of calim 46, wherein each of said plurality ofconductive contact sites comprises a flat surface.
 48. The apparatus ofclaim 46, wherein each of said plurality of conductive contact sitescomprises an indentation for receiving a portion of said at least onesolder ball of said ball grid array of solder balls.
 49. The apparatusof calim 46, wherein each of said plurality of conductive contact sitescomprises an indentation having at least one projection extendingthereinto.
 50. A testing apparatus for a semiconductor assembly having aball grid array of solder balls on a surface thereof, said apparatuscomprising: an insert formed of generally noncompliant material, saidinsert having a first surface including an array of conductive contactsites for contact with at least one solder ball of said ball grid arrayof solder balls and having a second surface; a substrate having a firstsurface and a second surface, said second surface of said insertattached to said first surface of said substrate, a pattern ofconductive leads on said substrate for connection to contact leads in asocket; electrical leads connecting said array of conductive contactsites of said insert with said pattern of conductive leads of saidsubstrate; a test board having said socket with said contact leads to atesting circuit, said substrate and insert insertable into said socketfor electrical contact of said pattern of conductive leads of saidsubstrate with said contact leads of said socket; heating apparatusassociated with one of said substrate, said insert and said socket; andpower supply leads providing electrical power to said heating apparatus.51. The apparatus of claim 50, wherein said heating apparatus comprisesresistance conductors.
 52. The apparatus of claim 50, further comprisinga switch apparatus for turning said heating apparatus on and off. 53.The apparatus of claim 50, further comprising temperature sensingapparatus attached to one of said substrate, said insert, and saidsemiconductor package.
 54. The apparatus of claim 53, further comprisinga temperature controller receiving signals from said temperature sensingapparatus and controlling said heating apparatus.
 55. The apparatus ofclaim 53, wherein said temperature sensing apparatus comprises athermocouple junction.
 56. The apparatus of claim 50, wherein saidheating apparatus includes a conductive layer of metal deposited on oneof said first and second surfaces of said substrate.
 57. The apparatusof claim 50, wherein said heating apparatus, said power supply leads andsaid array of conductive leads are formed on said substrate.
 58. Anapparatus used to temporarily connect at least one solder ball of aplurality of solder balls of a solder ball array on a first member to atleast one corresponding contact site of a plurality of contact sites ona second member, said second member attached to a third member, saidapparatus comprising: a board having a socket thereon for accepting saidfirst member, said second member, and said third member, said boardhaving at least two through-holes extending therethrough and havingfirst and second through-hole axes generally perpendicular to saidbroad; at least one heating conductor mounted on an underside of saidthird member, said at least one heating conductor having junctionspositioned intercepting said through-hole axes of said firstthrough-hole and said second through-hole extending through said board;a spring-loaded pogo pin moounted to project a pin portion upwardlythrough each of said at least two through-holes of said board to contactsaid third member; and power leads connecting said spring-loaded pogopin to a power supply for heating said first member, second member, andsaid third member including said at least one solder ball of saidplurality of solder balls of said solder ball array and said at leastone corresponding contact site of said plurality of contact sites. 59.The apparatus of claim 58, further comprising a temperature sensormounted within said first, second and third members and conductivelyconnected to a temperature measuring circuit.